A coincidence is generally considered (by the dictionary) to be some sort of event which happens without a causal connection. Hopefully diligent readers of this site have started to learn that the dictionary lies. Experience tells us things generally happen in two ways; with causal connection we know how to define, or with apparent randomness. In this last scenario, it seems reasonable that randomness is an illusion created by imperfect human information. To call upon a simple example; if I know the initial conditions of a particle (location, velocity, acceleration, time) I can predict with perfect accuracy the trajectory of the particle under classical mechanics. Conceal some of these initial conditions from me or introduce a force I am unaware of and my predictions are wrong. Is the particle moving with random motion? Clearly not – this is a trivial example to highlight the introduction of “randomness” as a result of poor knowledge. When we extend to less trivial systems (quantum mechanical, for example) our intuition would tell us that the same logic applies – but there are additional complexities (such as the measurement and observation problem) which mean we cannot state this with certainty.
The universe is a curious place – if it wasn’t we wouldn’t need to rationalise it so this site would have never been set up. So the curiosity of the universe is a necessary condition for you to be reading the to question the universes curiosity. Hold that logic for later. One of the most interesting things about the universe is the seemingly endless list of finely balanced parameters without which life couldn’t have developed. First we outline some of the most startling coincidental results of the universe, before deciding if we should place any credit on an idea that “explains” them all- the anthropic principle.
The Higgs boson
The Higgs boson is the particle named after British physicist Peter Higgs, based at Edinburgh university and now retired (although ever active in the world of particle physics). The Higgs boson is sometimes deemed to be the “mass giver” to particles; which can only really be understood by considering the the associated Higgs field (what is a field?). As a particle passes through the Higgs field, mass is “given” to the particle – a process which also impacts the mass of the Higgs boson. The heavier the particle, the heaver the mass of the Higgs boson and vica versa- so when a top quark interacts, the heaviest of the quarks, the Higgs boson has the greatest mass.
The Higgs boson revealed some interesting features around vacuums – namely the fact that a vacuum indeed has lots of energy.The Higgs field is often depicted as having a Mexican hat shape as seen below, with the point of the hat centered on 0. It is rather interesting – the Higgs field works with having the maximum energy in the massless state, as depicted in the below illustration of the field. So now if a particle were to enter the vacuum, this energy would be transferred to it giving it mass; if that interests you I recommend some reading on the energy of empty space.
The relationship between the heaviest particle in the universe and the Higgs boson is very important; since it is the interaction of the Higgs field and the heaviest particle that alters the mass of the Higgs boson. It seems that if the top quark were slightly heavier, the universe would be unstable an collapse. This graph marks our likely position, although I should note that measurements of this nature are fraught with difficulty, so it is possible that the location is a little different.
As you can see – we are rather precariously placed in the metastability section; frighteningly close to the instability. What this means for the universe is if we had an additional quark, a larger one, or indeed the mass of the top quark was a little heaver we would be kindly nudged into the instability section, goodnight universe. Why should the largest particle have stopped at such a point that the mass did not tip the universe into the dangerous area of instability? Are we just “lucky”?
The flat universe
Einstein showed us that matter and energy distort space and time – which has profound implications for the shape of the universe. The density of any given universe will determine if eventual outcome, most of which are fairly unappealing. If the density is very low then the universe curves up and outwards infinitely expanding. Whilst this might seem excellent news for the inhabitants, death in the universe arrives as the universe constantly cools with the expansion, leading to a realm with no meaningful energy. The second option is that the density is really high, in which case the universe bends inwards. In this scenario, we have a much more dramatic ending – the universe finishes pretty much back to where it started. The matter is eventually pulled back in with the irresistible lure of gravity and crunched up into a little ball (of infinite mass and density – headache). The final option is the perfect medium – hitting the sweet-spot in which the universe does not bend, with expansion eventually tending to zero as time tends to infinity. Get me one of those. Well actually, we might have one.
The value omega is used to denote the value we are interested in – the number that determines the eventual fate of the universe. For a fuller description, see the flatness problem, but in short greater than one is the crunch, less than one is the big chill and one is deal. Cosmologists currently believe our value is astonishingly close to 1 – although we would need to be sure it was exactly 1 to have the perfect universe. Current calculations vary from 0.1 to around 1; but the most accurate seem to be settling around 1. What is most astounding is is the sensitivity of omega around one second after the big bang – if you were to tweak this value by just the smallest amount as shown by the below graph the outcome is very different. If omega was a tiny fraction smaller, or a tiny fraction larger we would be in trouble. Why should we be so lucky to have this value, 1 or close to it? It’s a bit like trying to balance a knife on its point for the duration of the universe (don’t invest any time trying this).
A few final coincidences
There are a number of other coincidences that seem to evade logic and rationale. For example we largely believe we have many different dimensions in the universe, however there are only three spacial dimension we experience. How many dimensions you think exist depends on you hymn sheet; but the current brand of superstring theory requires 10. Whilst the number does vary – the common consensus emerges that the number is greater than the spacial dimensions we can traverse. For many reasons it is theorised that life could not exist in two or four spacial dimensions; so why were we fortunate enough to have three?
There deeper and more confusing ratios to ponder – for example the fundamental interactions. The ratio between electromagnetism and gravity is in a fine balance; if it were to be smaller then we wouldn’t expect a universe to live for every long. The ratio of gravitational energy required to pull a galaxy apart compared to its mass energy – again if this is a little out stars either do not form or they do not survive which would mean no elements being cooked up and ultimately no me and you.There are so many “coincidences” in this big universe of ours that listing them all results in one very long list of facts. The biological ability of carbon, the properties of water, the atmosphere of the Earth, the color of the sun and so grows the list.
Hopefully what is clear is that there are a huge number of factors that if we were to adjust in a very small way would result in total destruction of the universe, or an inability for life to form. If you were a gambler, you would never have put any money on our universe existing the way it does (if you could retrospectively gamble before your existence – probably not a business venture) . So if it is really improbable, why is it so?
Perhaps this section would more aptly named, further considerations. I read a feature recently on an unnamed blog which raised a philosophical point – the anthropic basis. The headline of this theory is things exist as they are because if they did not you would not exist to pose the question. It is very circular logic – and this is intentional. It is argued that the conditions in the universe have to be favorable for the beings posing the question of why the conditions are the way they are – and therefore it is unsurprising to find the conditions the way they are. For example, life would never have appeared earlier than it did because the stars would not have had time to cook up the elements. But on the other hand life wouldn’t have arrived a large amount later, because if this were the case the stars would be dead. So life could only of arrived at this opportune moment.
You can apply this logic reasonably successfully to a number of different coincidental results – for example if the mass was heavier of the top quark then you wouldn’t be here to pose the question – therefore you can only ask the question of why the top quark has that mass precisely because the top quark has that mass. This is actually the weak anthropic principle – there is a strong anthropic principle along with a whole host of other takes on the anthropic basis; unlike a law we don’t have the luxury of precision. If it is of interest I would suggest you do some further reading – I am not going to discuss any more. Why?
I think it’s a little cheap? It is an interesting idea but there are some severe issues with this theory. There are for example, various things that could have occurred which meant that our universe was only capable of inhabiting intelligent life for a much shorter length of time than it is. We would have still been around to pose the question; we just might not have felt quite so lucky. There also isn’t much account taken for the various different life forms that could exist – we are interested in why things are exactly the way they are. If you start to flex the anthropic principle with statistics you end up negating it’s very own logic.
My more favored explanation is that the factors inside our own universe are ever so rare – highly improbable but nature has many bites at the apple. If you are to accept a multiverse, then it is feasible that if our universe had a one in a billion chance of creation (illustrative, the probability is lower), but there have been two billion attempts you might start to ask where the hell is the other one. Statistics often give the illusion of fairly random results when performed a small number of times – but roll the dice millions of times and the whole thing starts to look delightfully predictable. Anything that can happen will happen. In fact the mathematics is seducing us in this direction; it is a funny thing when you find mathematics that can feasibly explain your own universe, but also suggests there should be many many others. To ignore the signs given by mathematics is to walk across a motorway with your eyes shut.
If you have not read it, I would recommend Mekhi’s account of the bubbles of the multiverse, which argues perhaps all of the uniqueness we perceive is an observational bias of the universe in which we are stuck.